I was already on record as expressing scepticism about Neil deGrasse Tyson’s forthcoming Cosmos television series, as I view his knowledge of the history of science as at least as bad if not worse than Carl Sagan’s was and that was pretty terrible. Yesterday evening my Twitter stream was full of people wondering what I would have thought of N dG T’s elevation of Giordano Bruno to the status of a great scientific thinker. Fortunately I can’t view Cosmos here in Germany and so I was spared this particular piece of history of science inanity. However I came across another wonderful example of N dG T’s fantasy version of the history of science today.

Massimo Pigliucci’s Rationally Speaking has a new podcast interview, Neil deGrasse Tyson on Why He Doesn’t Call Himself an Atheist. Tyson rejects the label atheist because of the expectations that radical atheists place on him, an attitude that I can more than sympathise with. The particular trigger for this discussion was Tyson being volubly criticised for using the expression god speed in a video, which he quite rightly regards as being an imposition. In the course of the discussion Tyson then goes on to list other Christian things that he likes, uses, accepts despite not believing in the Christian God. Again I have no argument with him in this. However he then let off a minor tirade about the calendar and those who reject the use of AD/BC.

Tyson’s argument was roughly as follows, The Gregorian Calendar is a great invention and should be respected. It was a Christian invention, created by Jesuit scientist. Accept it! (A paraphrase not a direct quote) This brief outburst contains a whole series of historical errors that are unfortunately typical for Tyson.

First off his main bone of contention the origins of the AD/BC dating system has nothing to do with Gregorian Calendar. The use of Anno Domini goes back to Dionysius Exiguus (Dennis the Short) in the sixth century CE in his attempt to produce an accurate system to determine the date of Easter. He introduced it to replace the use of the era of Diocletian used in the Alexandrian method of calculating Easter, because Diocletian was notorious for having persecuted the Christians. Dionysius’ system found very little resonance until the Venerable Bede used it in the eight century CE in his Ecclesiastical History of the English People. Bede’s popularity as a historian and teacher led to the gradual acceptance of the AD convention. BC created in analogy to the AD convention didn’t come into common usage until the late seventeenth century CE. There is a certain irony in the fact that Dionysius miscalculated the birth of Christ who was most probably born sometime between six and four BCE. Whatever, the AD/BC dating convention has nothing to do with the Gregorian Calendar, although this did take it over.

Tyson’s little outburst however contains more historical errors. The Gregorian Calendar is indeed a Christian invention but it was not created by Jesuit scientists. First off to refer to anybody who existed before 1834 as a scientist is a historical anachronism to be avoided if at all possible. Personally I’m coming to the conclusion that the word scientist should be generally avoided, as it’s a highly ambiguous word, but that is the subject for another post. The people who created the Gregorian Calendar should be referred to as astronomers. Calendar creation and calculation has been the task of astronomers since the early years of antiquity.

Unfortunately for our intrepid science communicator the Gregorian Calendar was not created by the Jesuits. The original scheme for the calendar was worked out by Aloysius Lilius (vernacular either Luigi Lilio, or Luigi Giglio) who was a physician and astronomer from Calabria in Italy. Lillius was not a cleric of any sort let alone a Jesuit. His scheme was examined, contemplated and finally recommended by a committee that met irregularly over a period of more than ten years. The exact composition of this committee is not known, as it varied over the years, but nine members signed the final recommendation to the Pope of whom only one, the least significant member Christoph Clavius, was a Jesuit. Following the introduction of the calendar by the Catholic Church Clavius, at the request of the Pope, took over the defence of the new system of time measurement against its many critics, writing six books on the subject over the next thirty odd years, thus becoming closely associated with the calendar although he did not create it.

These are all facts that are easily accessible to anybody with use of a good library or who knows their way around the Internet (hint, hint Wikipedia!) and there is absolutely no excuse for Tyson to spout his fully incorrect version of history, which will unfortunately be accepted as gospel by his army of worshipers.

Addendum: Both the Jewish and the Islamic calendars are older than the Gregorian calendar so why should these two non Christian peoples accept the AD/BC dating convention? There are other older calendars in use in India, China, Persia, same argument. Also the Gregorian calendar is only a slightly modified version of the Julian calendar, which was distinctly non Christian and it was nothing more or less than the Egyptian solar calendar in use since about four thousand BCE, again anything but Christian.

29 responses to “Where does the AD/BC dating convention come from?”

The term scientist is anachronistic applied to anybody before 1834 and fairly meaningless applied to anybody afterwards.
The term science was already in common use as the English translation of scientia meaning knowledge in the sixteenth century, so yes.

‘Twere better to fight about arbitrary symbols with a little more substance, like Tungsten vs. Wolfram. At any rate, it’s hardly worth the pretension of the extra byte, since folks of certain persuasion in the U.S. have long maintained an occult tradition of syntacking CE with the semantics Christian Era.

Great post, Thony, I really hate it when people can’t tell apart calendars and eras (a scientist really should know better!). Unfortunately, the new “Cosmos” looks like it’s going to be full of disgusting howlers, with Giordano Bruno only being the first salvo.
BTW There are of course instances of BC-dating in late medieval chronicles, but I suppose you are perfectly right about “common usage” from the seventeenth century onward. I am personally skeptical as to whether it’s fair to say that Dionysius Exiguus “miscalculated” the birth of Jesus, although this is a very common claim. In my view, there is no sufficient reason to think that Dionysius calculated at all (rather than following a dating or era already in use) and no sufficient evidence to support any particular date for Jesus’s birth. The view that he was born in 6-4 BCE is based on a fairly naive acceptance of the nativity stories in Matthew and Luke according to which Jesus was born during the reign of Herod. Given the devastating historical and textual criticism these stories have been subjected to, I think it is likely that Herod makes an appearance for purely typological reasons (he is the Pharaoh to Jesus’s Moses) and that the author of this story had no genuine knowledge of when Jesus was born. It thus could well be that the Dionysiac era is correct by sheer coincidence.

Well there is a claim (*) that year 1 arose from Essene/Qumran thinking about time and expected events, and predates Jesus. There is also the claim that monasteries existed before Jesus, and that they transferred a lot of knowledge and ideas secretly forward. So that could be how year 1 got from the Essenes to Dennis the Short. It would also explain why it is patently nothing to do with the birth of Jesus which has to overlap with Herod the Great.
(*) Dare I mention that great Aussie code breaker Barbera Thiering?

That sounds like a load of nonsense to me. Does Thiering (has she ever passed peer review even once in her life?) have any actual source evidence to back up her claim? I doubt it. Why would Dionysius need any obscure and unproven link to Qumran if we have a whole tradition of Christian chronography to contextualize the emergence of the Christian era (see, e.g., Mosshammer, “The Easter Computus”?). Who says the era has “nothing to do with the birth of Jesus”? Dionysius Exiguus clearly thought it did. Also, there is no sufficient reason to believe that Jesus’s birth historically had to overlap with Herod the Great. That’s just a naive acceptance of Gospel writers’ Midrash.

Marinus Taisbak pointed out some time ago (in 2000, in an article for MAA Focus) that Dennis’s date is best explained by his goal of getting the date of Easter right. To tie together the Lunar and Solar cycles it’s best if you start with a year date divisible by the right numbers. Dennis also knew that it had been about 500 years. So he picked the unique number in the 500s with the desired divisibility properties. That sounds more plausible than any attempt at historical calculation.

That theory shows a complete ignorance of what Dionysius Exiguus actually stated himself and how his Easter table fits into the late antique tradition of Easter reckoning, which goes back to Alexandria. Dionysius Exiguus didn’t invent any new Easter cycle. Taisbak has obviously no idea what he’s talking about and there is nothing “plausible” about this. Quite on the contrary, late antique Christian authors engaged in historical calculations all the time.

Woop-dee-doo, you may not have mentioned a new Easter cycle but this the only way this argument could even begin to make sense. The fact of the matter is that Dionysius Exiguus worked with an existing cycle and that what you call “lunar tables” is simply the continuation of a previous Easter table in the Alexandrian tradition. To label the first year of that continuation as “AD 532″ instead of “248th year of Diocletian” would have brought no computational advantage, especially since AD 1 is not the beginning of any relevant cycle. The sentence “To tie together the Lunar and Solar cycles it’s best if you start with a year date divisible by the right numbers” is nonsensical and reflects nothing that is any way relevant to late antique computistical practice. This whole argument appears to be just another case of someone noticing that 532 is a multiple of 28 and 19 and deciding that this must be significant somehow, because…well, just because. Fortunately, historians don’t argue like this. They look at evidence.

Thony said:
“I was already on record as expressing scepticism about Neil deGrasse Tyson’s forthcoming Cosmos television series, as I view his knowledge of the history of science as at least as bad if not worse than Carl Sagan’s was and that was pretty terrible. Yesterday evening my Twitter stream was full of people wondering what I would have thought of N dG T’s elevation of Giordano Bruno to the status of a great scientific thinker. Fortunately I can’t view Cosmos here in Germany and so I was spared this particular piece of history of science inanity.”

Although I quake in terror at submitting this link, in fear it might be riddled with historical errors, here’s a short piece I wrote about the ‘AD’ dating system as my (unsuccessful) entry in a Secular Thought for the Day competition:

“Yesterday evening my Twitter stream was full of people wondering what I would have thought of N dG T’s elevation of Giordano Bruno to the status of a great scientific thinker.”

The show made it pretty clear Bruno’s issues with the Church were largely theological, and that while he saw support for his views in Copernicus, his beliefs came from his own philosophical and religious musings and visions. I’m pretty sure they say he was an original thinker, not a scientific one. So I don’t think there’s too much reason to get angry about it.

I’ll be writing a guest post for Renaissance Mathematicus on the (literally) cartoonish caricature of the Bruno story in *Cosmos* and the clumsy rhetorical point the program seems to have been trying to make. It should be up by early next week. It will detail why the misuse of the Bruno story is a sore point for historians of science and why the perpetuation of myths in this program annoys people who actually take history seriously rather than wanting to use it to create neat little fables.

I was inclined to agree with you, simplicio, but I just saw it and it is really bad. Personally, I don’t think Bruno was a bad character to focus on per se, and he might have been used to demonstrate the idea that there weren’t any “scientists” in 1590, and that there were always lots of creative ways to imagine the cosmos. But they butcher it. The bad accents make the whole thing unintentionally hilarious and the general presentation of Bruno being laughed at and chased off by unthinking dogmatists all over Europe, while trying to persuade people that their “god is too small” would be a huge red flag in front of all the thinking Christians I know.